1. Field
The present invention is concerned with the production of reformed cracked gasoline in a combination process employing catalytic hydrocracking and catalytic reforming stages. A novel stabilized catalyst containing a silica-alumina cracking base component is employed in the catalytic cracking stage. The cracking base component is of the simultaneously coprecipitated cogel-type.
2. Prior Art
The prior art abounds with methods for the production of catalysts comprising a metal associated with the surface of a porous inorganic oxide support. In accordance with the prior art, said catalyst can be produced in a variety of ways, for example by impregnating a preformed inorganic oxide carrier with the metal or by coprecipitating the metal as an oxide or hydroxide along with the materials forming the porous inorganic oxide support; for example, the pH of a solution containing dissolved silica, alumina and palladium can be adjusted to the point where the silica and alumina coprecipitate and the palladium is chemisorbed to a limited extent onto the resulting silica-alumina coprecipitate, said palladium being primarily in the form of soluble palladium hydroxide and/or palladium salts. The palladium does not coprecipitate along with the silica and alumina, since the palladium cation and, more particularly, palladium hydroxide, are soluble at pH's within the range that silica and alumina coprecipitate.
The preparation of cogelled silica-alumina cracking catalyst base components and catalytic cracking components by simultaneous precipitation is described in U.S. Pat. No. 3,280,040.
U.S. Pat. No. 2,662,861 teaches preparing: (1) a slurry of alumina, washing it, adding a promoter, bubbling hydrogen sulfide through (2) a solution of chloroplatinic acid hexahydrate, mixing (1) and (2) together and drying to form a catalyst. A similar process is disclosed in U.S. Pat. No. 3,617,509.
U.S. Pat. No. 2,898,305 teaches mixing silica in a slurry form with an insoluble inorganic compound, drying and calcining.
U.S. Pat. No. 2,688,603 teaches catalyst preparation by distributing an organic compound containing a potentially catalytically active metal on the surface of a suitable support and decomposing the organic portion of the molecule.
U.S. Pat. No. 3,210,296 teaches impregnating an inorganic oxide support by use of a noble metal compound dissolved in an alcohol, ether, aldehyde, ketone, or mixtures thereof.
U.S. Pat. No. 3,801,515 teaches preparing a finely divided metal by reducing a metal-containing compound in an aqueous medium and intimately intermixing the metal with a gelatinous precipitate. It has been surprisingly discovered that when catalysts comprising a noble metal of Group VIII associated with a porous inorganic oxide support are prepared by the method of the present invention, a larger proportion of the metal, preferably palladium, attempted to be incorporated into said catalysts is actually incorporated therein than is obtained by the prior art coprecipitation-plus-chemisorption method of catalyst preparation. It has also been surprisingly discovered that when a catalyst is prepared according to the present invention the resulting catalyst exhibits exceptional catalytic hydrogenation stability. It is believed that the high catalytic hydrogenation stability found for the catalyst prepared in accordance with the present invention is the result of a more uniform and possibly more specific dispersion of the metal upon the surface of the porous inorganic oxide support than is ordinarily obtained.